Oil on pistons

Post by **Tweedy** » Sat Sep 12, 2009 10:48 pm

Hi All
I am still having the same problem with oil getting all over the pistons and and then burning oil someone said it could be the oil return holes on the pistons that are choked up, could anyone tell me where abouts they are so I could check them please.
Thanks
Bob

Post by **bmcecosse** » Sat Sep 12, 2009 11:04 pm

Highly unlikely! They are in the ring grooves - so it would be pistons out, remove rings, probe holes. The problem will be pressure in the crankcase - caused by 'blow-by' down the worn bores/possibly stuck rings. Test by running the hot engine - and taking the oil filler cap off. Plume of smoke/fume confirms. Make sure one of the breathers is connected directly to the carb - to remove at least some of the fume !

Post by **MarkyB** » Sun Sep 13, 2009 7:48 am

These holes do get blocked, they were in my engine.
However it didn't lead to oil on the pistons.
I'd go along with what bmcecosse says and add be prepared to take the head off and examine the actual condition of the bores.

Post by **bmcecosse** » Sun Sep 13, 2009 10:14 am

You could of course try the trick of flooding some diesel fuel into each bore - and letting it sit there with gentle turning and refreshment for a few days!

Post by **MarkyB** » Sun Sep 13, 2009 6:03 pm

Spin it over with the plugs out before you start the engine though.
Put some rags over anything you don't want sprayed and be prepared to lay down quite a smoke screen for a short while.

I'd change the oil soon afterwards too.

Post by **Tweedy** » Sun Sep 13, 2009 7:39 pm

Thanks to everyone I will start on these tasks tomorrow, and I will buy some more oil, it will be nice to get her right again the engine runs great its just the oil smoke when she gets warm and the oil on top of pistons.
So thanks again
Bob

Post by **rayofleamington** » Mon Sep 14, 2009 7:45 pm

It may end up a quicker solution to strip the engine and clean/replace rings where needed.

Post by **Tweedy** » Mon Sep 14, 2009 7:51 pm

Hi Ray
Would I be able to strip the engine without taking the engine out
Thanks Bob

Post by **bmcecosse** » Mon Sep 14, 2009 8:21 pm

You can certainly push the pistons out the bores and work on them on the bench.

Post by **rayofleamington** » Mon Sep 14, 2009 11:20 pm

yes - the sump can come off to give access to the bottom end, and with the head off the pistons should come out of the top.
I'd be tempted to remove the head first of all to inspect the bores. If the bores are excessively worn or damaged / scored then there's not much point continuing.
If the bores look ok, then you're in with a very good chance of getting it fixed.

When big ends are released, make sure you note which caps go where (should be marked already but DO check + make notes) and also which pistons are which!

As for not removing engine - it is a viable option but for this much of a strip down you'll not save any effort. Jobs like refitting the sump can become fiddly when you're working under a car due to gravity and limited light.

Post by **Tweedy** » Wed Sep 16, 2009 8:16 pm

Hi Ray
Thanks for all the info,will have a go.
Bob

Post by **leyther8008** » Thu Sep 17, 2009 8:05 am

Try new valve stem oil seals first thats usually where oil get down into the bore from, especially after standing and a lot of smoke on first start up. or on closed throttle descending a long hill then when you open the throttle again its like a scene from 'sink the bismark' (make smoke).

Post by **Tweedy** » Thu Sep 17, 2009 9:50 am

Hi
I have put new oil seals on and it as made no difference do you think it could be the stems, also I have taken the head to be skimmed which they did but they couldn't do a compression test so I dont know whats the matter with it,so thanks for info.
Bob

Post by **bmcecosse** » Thu Sep 17, 2009 10:00 am

It's never the valve stem seals! Plume of smoke = worn bores/stuck rings

Post by **Tweedy** » Thu Sep 17, 2009 10:16 am

Thanks Roy

Post by **bmcecosse** » Thu Sep 17, 2009 10:58 pm

Sorry to be harsh Tweedy - many cling to the straw of 'valve stem seals' - but unless they are not there at all (PO neglected to fit them) - they won't be the source of any worthwhile smoke plume. Still worth popping the pistons out and inspecting /freeing off the rings - provided you are confident of getting them back in the bores without breaking them!

Post by **Tweedy** » Fri Sep 18, 2009 6:02 pm

ok will have a go Roy.
Bob

Post by **rayofleamington** » Sat Sep 19, 2009 10:30 am

It's never the valve stem seals!

I disagree - I've had one with a very worn head that gave a lot of smoke after engine braking. It was cured by changing the head, as the route cause of the leaking seals was the worn valve guides.

However I'll second what roy said for this case - even without stem seals the top end leak won't be enough to drown the engine.

Post by **Tweedy** » Sat Sep 19, 2009 6:24 pm

ok thanks to all

Post by **bmcecosse** » Sat Sep 19, 2009 8:56 pm

Ahh - that was worn GUIDES (and possibly stems) - not same as seals !